This invention relates to a process for producing a controlled release preparation, more particularly to a process for producing a controlled release preparation which volatilizes drugs or active agent such as an insecticide, an attractant, a repellent, a pheromone, an insect controlling agent, a bactericide, flavor and a deodorizer, little by little over a prolonged period of time, which are widely employed in the agricultural, domestic and business fields.
Various methods have been proposed to control the effect of an active agent or of a drug over a prolonged period of time even when it is administered in small amounts (release controlling method). Namely, there have been known methods to use a hollow tube (U.S. Pat. No. 4,017,030, Japanese Provisional Patent Publication Nos. 142202/1981, 9705/1982, 45101/1982, etc.); to employ a microcapsule (U.S. Pat. Nos. 2,800,457, 2,800458, 3,577,515, etc.); and to employ a laminated film (American Chemical Society; 33 (1976) pp 283), etc.
However, in all of the above methods, preparation processes are so complicated and costly that they suffer significant disadvantage in providing controlled release drugs for uses particularly in the agricultural and domestic field. Namely, in the above method employing a hollow tube, filling and packing processes are complicated and costly, and also in the above method employing a microcapsule or a laminated film, the manufacturing process is complicated and costly. Also, there may be mentioned a method to use a solid composition (Japanese Provisional Patent Publication Nos. 95101/1981 and 113102/1983), wherein release controlling effect is achieved by use of a film formed by heating a solid and a resin. However, any of methods described above includes a complicated manufacturing processes, and thus is liable to be costly.
Thus, the present inventors have made extensive studies in an attempt to provide a controlled release preparation at low costs, and as a result accomplished this invention.